1. Field of the Invention
The present invention relates to a method of and an apparatus for producing area signals in a digital image processing system. More particularly, the present invention relates to a method of and an apparatus for producing area signals for designating a local area of a video image required for local video image editing or color transformation in a digital color image processing system such as a digital color copier or digital color printer.
2. Description of the Prior Art
FIG. 1 shows a schematic construction of a digital color copier as a gypical example of a digital color image processing system.
As seen from FIG. 1, such a color copier is substantially divided into six main parts. That is, the copier system includes a control unit 100 functioning to control an operation of the system, a scanner 200 for reading out a color video image of a document under a control of the control unit 100, an image signal processor 300 for processing the image signal supplied from the scanner 200, an image outputting unit 400 such as a laser beam printer for outputting a copied color image, a digitizer 500 for designating an area of the image for an image editing function and a color transformation function and a control panel 600 for interaction between an user and the system.
FIG. 2 shows a block diagram of a construction of the image signal processor 300 in FIG. 1. Analog image data signals which are simultaneously supplied from CCD (charge coupled device) sensors 201 in the scanner 200 are converted into digital image data signals by means of an analog to digital converter 202 and the digital image data signals are then entered to the image signal processor 300.
The image data from the analog to digital converter 202 in the scanner 300 are temporarily stored into a color decompositing and compositing portion 301 in the image signal processor 300 which puts the image data into the amount of data on a scanning line in a main scanning direction and serves to separate B (blue) data, G (green) data and R (red) data of the image data.
A shading correcting portion 302 which receives the B, G and R data from the color decompositing and compositing portion 301 functions to correct errors resulted from a degree of ununiformity of the CCD sensor 201 and a degree of ununiformity of a lighting source, for example, a fluorescent lamp which is disposed in the scanner 200 for irradiating the document. An algebraic correcting and complementary color converting portion 303 effects an algebraic correction of the data supplied from the shading correcting portion 302 to maintain a linearity in image data process and, simultaneously, converts the B.G.R signals into Y (yellow), M (magenta) and C (cyan) signals.
A black generating portion 304 functions to generate a black (BK) signals from the three Y.M.C colors, and a color correcting portion 305 corrects the degree of density of the respective color level in conformiting with the respective filters and toner and, simultaneously, outputs only the density signals of the color (one of the Y.M.C, BK color) which is developing by the image outputting portion 400.
A color transformation portion 306 performs a data processing function, that is a designated color transformation, a painting process, a trimming process or a masking process, which is selected through the control panel 600. A density processing portion 307 converts the image data supplied from the color transformation portion 306 on the basis of information (a copying density, a color balance and etc) provided from the control panel 600. A magnification and movement processing portion 308 effects an image magnification changing process and movement process in the main scanning direction by changing the input or output timing of the image data. A sharpness processing portion 309 allows to obtain an image corresponding to the value of a sharpness, mode designated through the control panel 600.
A document position recognizable portion 310 detects the position of the document located on a document stand and an area signal producing portion 311, which underlies the present invention, produces an image signal corresponding to the area designated by the digitizer 500 and supplies the image signal to the black generating portion 304, the color correcting portion 305, the color changeable portion 306 and the density processing portion 307.
FIG. 3 shows a conventional image signal producing circuit which is disclosed in Japanese laid-open patent publication No. sho 63-12055. Now, the circuit will be described in detail with reference to FIG. 3b showing a memory map and image signal generating timing chart in a conventional art.
Assuming that area signals AREAO to AREAn are generated, in a case of the area signal AREAO bits "0" of addresses X1 and X3 a RAM are written with "1" while all of bits "0" of the remaining address are to be "0". In a case of the area signal AREAn, bits "n" of addresses 1, X1, X2, X4 are written with 1 while all of bits "0" of the remaining addresses are to be "0".
As data are sequentially read out from memory devices in synchronizing with a constant clock signal which is generated on the basis of a horizontal synchronizing signal HSYNC, the data "1" can be read out at addresses X1 and X3 and then entered to both input ends J and K of the respective flip flops 148-0 to 148-n shown in FIG. 3a so as to toggle the output of the flip flops 148-0 to 148-n.
In FIG. 3a memory devices, such as RAMs generally designated 136 and 137, respectively which rapidly change the area signals. While the area signal data of the presently processing line is read out from the A memory 136, the B memory 137 is subjected to write the area data of subsequent line. The memory writing and reading operations are alternatively carried out to the A memory 136 and the B memory 137.
More specifically, when the states of control signals applied to control ports C3, C4 and C5 are to be 0, 1 and 0, the output of a counter 141 which is synchronized with the video (or image) clock V.sub.CLK is entered through a selector 139 to the A memory 136 as an address Aa. Accordingly, a gate 142 is opened while a gate 144 is closed, and n-bit data are supplied from the A memory 136 to the flip flops 148-0 to 148-n which produce area signals AREA0 to AREAn. At that time, a data write operation to the memory B 137 is simultaneously effected. That is, the data input through a data bus D-bus is written at an area of the B memory 137, which is designated by an address supplied through an address bus A-bus in accordance with a memory access signals R/W.
On the contrary, to generate a section signal from the data stored in the memory B 137 the control signals from the control ports C3, C4 and C5 are to be 1, 0 and 1 and the A memory 146 is subjected to the data writing operation while the B memory 137 is operated under the data reading operation.
According to such a conventional art (referred to FIG. 3) previously described, memory map is prepared by a central processing unit (CPU) which is constructed in the control unit 100 of FIG. 1 in accordance with the output of the digitizer 500 for designating a desired image area. Under this state, when an address of a sub-scanning direction corresponding to the memory map is input, the data related to the scanning line of the sub-scanning direction is written to the memory and the area signals AREA0 to AREAn are produced on the basis of the data stored in the memory.
With such a conventional construction, two memory elements which are changed on the basis of the horizontal synchronizing signal HSYNC are essentially employed so as to the area signals. That is, one of the memory elements serves to produce an area signal while the other serves to store data of next line under the central processing unit. The memory elements are alternatively subjected to an area signal output or data store.
In the conventional construction described above, the memory elements must be accessed through the address bus and the data bus by the central processing unit as the horizontal synchronizing signal is produced, so the operating speed of the system is likely to be decreased. Further, a separative memory is needed for storing and retaining data to be written into the two memory elements.